Material shifts shape using heat and light

A material developed by engineers at the University of Colorado Boulder can transform into complex, pre-programmed shapes via light and temperature stimuli before reverting to its original form.

Christopher Bowman, Distinguished Professor in CU Boulder’s Department of Chemical and Biological Engineering (CHBE), said: “The ability to form materials that can repeatedly oscillate back and forth between two independent shapes by exposing them to light will open up a wide range of new applications and approaches to areas such as additive manufacturing, robotics and biomaterials.”

Previous efforts have used a variety of physical mechanisms to alter an object’s size, shape or texture with programmable stimuli. However, such materials have historically been limited in size or extent and the object state changes have proven difficult to fully reverse.

The CU Boulder material achieves readily programmable two-way transformations on a macroscopic level by using liquid crystal elastomers (LCEs), the same technology underlying modern television displays. The unique molecular arrangement of LCEs make them susceptible to dynamic change via heat and light.

To solve this, the researchers installed a light-activated trigger to LCE networks that can set a desired molecular alignment in advance by exposing the object to particular wavelengths of light. The trigger then remains inactive until exposed to the corresponding heat stimuli.

“We view this as an elegant foundational system for transforming an object’s properties,” said Matthew McBride, lead author of the study and a post-doctoral researcher in CHBE. “We plan to continue optimising and exploring the possibilities of this technology.”